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Kazuko Omodaka, Seri Takahashi, Akiko Matsumoto, Shigeto Maekawa, Shiori Suzuki, Yukihiro Shiga, Tsutomu Kikawa, Kazuichi Maruyama, Masahiro Akiba, Toru Nakazawa; Lamina cribrosa thinning in glaucoma and associated factors. Invest. Ophthalmol. Vis. Sci. 2016;57(12):832.
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© ARVO (1962-2015); The Authors (2016-present)
Recently, we reported a noninvasive, in vivo method to measure the thickness of the lamina cribrosa (LC) with swept-source optical coherence tomography (SS-OCT, Topcon Corp, Japan). We found significant thinning of the LC in patients with glaucoma (Plos One, 2015). In the current study, we describe a simplified version of our method, and report factors influencing thinning of the LC in a large group of glaucoma patients.
This study comprised 150 eyes, including normal (n = 22), preperimetric glaucoma (PPG; n = 28), and open angle glaucoma (OAG; n = 100) eyes. We used SS-OCT to obtain 3 x 3 mm cube scans of an area centered on the optic disc. Twelve radial B-scans were reconstructed from the 3D volume data where specially designed en-face viewer software was used to visualize the B-scan and en-face image to identify the lamina cribrosa. Then, using our new, simplified method, we superimposed 16 grid points (each 175 µm square, in a 4 x 4 array) on the center of the Bruch’s membrane opening and measured the LC thickness (LCT) at each point. We then compared averageLCT (avgLCT) to mean deviation (MD; measured with the Humphrey field analyzer SITA standard 24-2), circumpapillary retinal nerve fiber layer thickness (cpRNFLT), the vertical cup-to-disc (C/D) ratio, central corneal thickness (CCT), axial length (AL), intraocular pressure (IOP), and optic nerve head blood flow (represented by tissue mean blur rate: MBR).
We found that the measurement time for our technique was about 12 minutes. The avgLCT differed significantly in the groups (normal 267 ± 23 µm, PPG: 248 ± 12 µm, OAG: 233 ± 20 µm, P < 0.001). Moreover, the correlation coefficient between avgLCT and each measurement parameter was 0.46 for MD, 0.57 for cpRNFLT, -0.52 for C/D ratio, and 0.38 for MBR (all P < 0.001). A multiple regression analysis of independent variables showed that LC thickness significantly affected C/D ratio (β = -0.25, P = 0.020), MD (β= 0.29, P = 0.013), and MBR (β = 0.20, P = 0.034), but not age, AL, CCT, or IOP.
The parameters of our newly developed, simplified method of measuring avgLCT promise to reduce time during testing and enable the inclusion of a higher number of cases in future studies. Furthermore, our results suggest that thinning of the LC precedes visual field loss, and that risk factors for LC thinning include cupping formation and reduced blood flow.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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